CVE-2026-6757
Published: 21 April 2026
Summary
CVE-2026-6757 is a medium-severity Access of Uninitialized Pointer (CWE-824) vulnerability in Mozilla Firefox. Its CVSS base score is 6.3 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Drive-by Compromise (T1189); ranked at the 21.1th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SI-2 (Flaw Remediation) and SI-16 (Memory Protection).
Deeper analysis
CVE-2026-6757 is an invalid pointer vulnerability (CWE-824) in the JavaScript WebAssembly component of Mozilla products. It affects Firefox versions prior to 150, Firefox ESR prior to 140.10, Thunderbird prior to 150, and Thunderbird prior to 140.10. The issue stems from an access of an uninitialized pointer, which can lead to memory corruption when processing malicious WebAssembly content.
The vulnerability has a CVSS v3.1 base score of 6.3 (AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L), indicating that an unauthenticated remote attacker can exploit it over the network with low complexity but requires user interaction, such as visiting a malicious website or opening a crafted email in Thunderbird. Successful exploitation could result in limited impacts, including disclosure of sensitive information, minor modification of data, or partial denial of service due to application crashes or corruption.
Mozilla security advisories (MFSA 2026-30 through 2026-34) and the associated Bugzilla entry (bug 2013588) confirm the issue was addressed in the listed fixed releases. Security practitioners should prioritize updating affected Firefox and Thunderbird installations to mitigate the risk, as no workarounds are specified in the provided references.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-24098
Vulnerability details
Invalid pointer in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Memory corruption in browser/Thunderbird WebAssembly enables drive-by compromise (T1189) via malicious sites, client-side exploitation for execution (T1203), and phishing delivery (T1566) through crafted emails/attachments.
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Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly requires timely application of the vendor patch that eliminates the uninitialized pointer flaw in WebAssembly handling.
Enforces memory protection mechanisms that can block exploitation of the invalid pointer leading to memory corruption.
Provides controls over mobile code execution that can limit processing of untrusted WebAssembly content until the browser is updated.